Editing One-liner program (section)

===Perl===
Here are examples in the [[Perl]] [[programming language]]:
* Look for duplicate words
 perl -0777 -ne '<syntaxhighlight lang="perl" inline>print "$.: doubled $_\n" while /\b(\w+)\b\s+\b\1\b/gi</syntaxhighlight>' 
* Find Palindromes in /usr/dict/words
 perl -lne '<syntaxhighlight lang="perl" inline>print if $_ eq reverse</syntaxhighlight>' /usr/dict/words
* in-place edit of *.c files changing all foo to bar
 perl -p -i.bak -e '<syntaxhighlight lang="perl" inline>s/\bfoo\b/bar/g</syntaxhighlight>' *.c

Many one-liners are practical. For example, the following [[Perl]] one-liner will reverse all the bytes in a file:
<syntaxhighlight lang="bash">
perl -0777e 'print scalar reverse <>' filename
</syntaxhighlight>

While most [[Perl]] one-liners are imperative, Perl's support for anonymous functions, closures, map, filter ([[grep]]) and fold (List::Util::reduce) allows the creation of 'functional' one-liners.

This one-liner creates a function that can be used to return a list of primes up to the value of the first parameter:
<syntaxhighlight lang="perl">
my $z = sub { grep { $a=$_; !grep { !($a % $_) } (2..$_-1)} (2..$_[0]) }
</syntaxhighlight>
It can be used on the command line, like this:

 perl -e'<syntaxhighlight lang="bash" inline>$,=",";print sub { grep { $a=$_; !grep { !($a % $_) } (2..$_-1)} (2..$_[0]) }->(shift)</syntaxhighlight>' number

to print out a comma-separated list of primes in the range 2 - number.