Regexes & grammars

Substitution

Full

Replace matched text in place with s///, or every occurrence with s:g///.

s/pattern/replacement/ finds the pattern and replaces it. Applied with ~~ to a mutable variable, it edits that variable in place. By default it replaces the first match; the :g adverb replaces them all.

First match #

my $s = "foo";
$s ~~ s/o/0/;
say $s;

Output

f0o

Only the first o is replaced, giving f0o.

Global substitution #

my $s = "foo";
$s ~~ s:g/o/0/;
say $s;

Output

f00

Notes #

The target must be assignable — $s ~~ s/…/…/ mutates $s. To get a new string without touching the original, use the .subst method: "foo".subst("o", "0", :g).
The replacement side is a double-quoted string context, so it can interpolate — including the match's own captures, e.g. s/(\w+)/[$0]/.
Related adverbs: :i (case-insensitive), :g (global); they combine, e.g. s:g:i/…/…/.