Answer: How do I add commas to a number? contributed by Fastolfe See perlfaq5: How can I output my numbers with commas added?. In addition, that FAQ apparently used to include the following, contributed by Andrew Johnson, as well: sub commify { my $input = shift; $input = reverse $input; $input =~ s/(\d\d\d)(?=\d)(?!\d*\.)/$1,/g; return reverse $input; } [download]

Answer: How do I add commas to a number? contributed by Roy Johnson A lookaround method that will work on any numbers embedded in a string (but will not commify after a decimal point): sub commify { local $_ = shift; s{(?<!\d|\.)(\d{4,})} {my $n = $1; $n=~s/(?<=.)(?=(?:.{3})+$)/,/g; $n; }eg; return $_; } [download] If you prefer the FAQ rule of only working on things that begin with digits or -, sub commify { local $_ = shift; s{(?:(?<=^)|(?<=^-))(\d{4,})} {my $n = $1; $n=~s/(?<=.)(?=(?:.{3})+$)/,/g; $n; }e; return $_; } [download] This one does a single pattern match and then uses substr() to insert the commas: sub commify { local $_ = shift; if (/^-?(\d{4,})/g) { for (my $p=$+[1]; $p>$-[1]; $p-=3) { substr($_,$p,0) = ',' } } return $_; } [download]

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