On the basis of replace text with function ? and similar, a version of s///(g) that takes a code ref as the second half of the construct (somehow) and calls the subroutine with @_ aliased to the current captures:

sub transform (
   $_[ 0 ] = 'tripped';
}

...

$text =~ s[cow\s+(jumps)\s+over][\&transform]rg; ## /r for 'ref'?
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