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Search and replace the string 'this' with the string 'that' in the file filename. perl -p -i -e 's/this/that/g' filename #Perl #Trick #PerlOneLiner #Tipsoftheday #Replace #FindandReplace

Print all possible 2 combination of words ( ATGC): $letter = join',','A','T','G','C'; @abc=glob "{$letter}{$letter}"; foreach (@abc) { print "$_\n"; } #Perl #PerlTrick #TipsOftheDay

Get line number with Perl $fh->input_line_number() #Perl #Tipsoftheday #Tricks

regex (?(3)foo|fu)bar - Matches foo if 3rd subpattern has matched, fu if not #Tipsoftheday #Regex

Convert space separated data to tab separated: perl -p -i -e 's/\s+/\t/g' file.txt #Perl #Tipsoftheday #Perlonliner

To print the matching pattern line perl -ne '/pattern/ && print' infile.gtf #Perloneliner #Tipsoftheday

To count the number of matches in a string !!! $str = "one.two.three.four"; $n =()= $str =~ /\./gi; print $n; #Tipsoftheday #Perl

Number all lines in a file; perl -pe '$_ = "$. $_"': #Tipsoftheday #Perl

Generate N base genome: perl -e '@b=qw/A T G C/;print ">Genome\n";while($l<N){print @b[int(rand(4))];$l++;}' #Tipsoftheday #Perl

To round a floating-point value to a certain number of decimal places: $rounded = sprintf("%.2f", $unrounded); #Tipsoftheday #Perl

To get all the module dependencies for yourScript.pl program. $ scandeps.pl yourScript.pl #Perl #Tipsoftheday

To check: Does an array has all equal values. if (keys %{{ map {$_, 1} @test }} == 1) { # all equal } #Tipsoftheday #Perl

Write something at the bottom of the file without opening it. perl -p -i -e 'eof && s/$/\nWord/;' <filename> #Tipsoftheday #Perloneliner

Do you want to compile your Perl program without running it, try $ perl -c <program> #Tipsoftheday #Perl

print "$^O\n"; To print the OS name in perl #Tipsoftheday #Perl #RegularExpression