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Arrays
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push @arr, $x
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Add to end of array
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$x = pop @arr;
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Remove last element of array, put in $x
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shift @arr; (See also unshift)
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Remove first element of an arrray, put in $x
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$size = scalar @arr;
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Number of things in the array
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See also: split, join, splice, sort
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split string->array, join array->string, delete part of array, sort array in many ways
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scalar variables
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while (defined ($x=<>)) {code}
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False if variable has never been set (or when you try to read past the end of an input file)
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length($x)
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Length of a string
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chomp($line);
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Remove a newline at the end of a string
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$short=substr ($long, 2, 5)
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Characters 3-7 of $long (first char is 0!)
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Hashes
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@key = keys %hash
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The lookup terms in the hash
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if (exists $hh{“Hsp”}) {...}
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See whether hash %hh has a value for key Hsp
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Input/Output and Files
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open(HANDLE, ">outfile") or die “Can’t open $outfile: $!\n”
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Open outfile for writing, and associate it with filehandle HANDLE. Use “
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print $x; print HANDLE $x;
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Prints to standard output (screen), Print to filehandle HANDLE
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warn “Something wrong\n”;
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Prints to standard error (screen)
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$x=<HANDLE>
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Read a line from filehandle HANDLE, put in $x
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close(HANDLE);
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Stop reading/writing a previously opened file
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Exit
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exit;
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Exits the program
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die "Something broke!\n";
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exits the program with error message
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>> Operators and Loops
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>> Matching and Regular Expressions
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
