Perl

Things that do work

Searching and matching is explained in Regular Expressions.

Print out the contents of $variable in a structured format

use Data::Dumper;
print Dumper($variable);

if-then-else:

if < expr > {
 <codeblock>
} elsif < expr ) {
 <codeblock>
} else {
 <codeblock>
}

$var += <value>

Add <value> to $var (works for -, *, / too)

$string .= $addstring

Concatenate $string and $addstring

$string =~ s/<regexp>/<newvalue>/[g]

Substitute <regexp> with <newvalue> in $string. The g modifier makes the all occurrences of <regexp> are substituted.

$newstring = substr($string,start,length)

Return substring of $string

sprintf(format,$string)

Return formatted string. format is e.g. "%.3f". Check Python:Strings#Advanced for all formats.

$exitcode = system("a command")

Executed the command in a subprocess and return the exitcode

$output = `a command`

Execute the command and return all command output

Hashes

%newhash = (%oldhas1,%oldhash3)

Merge 2 hashes (works is all keys are unique)

Warning

If testing for existence of a hash key beware that all intermediate keys will be created by the test. In below example $hash1($key1} will be created if it does not exist yet.

if (exists $hash1{$key1}{$key2) {
    ...
} else {
    ...
}