I'm not sure if I understand you correctly, but maybe ...

In a regular expression, you can use variables as well: $variable =~ s/($pattern)+/..../ Beware that $pattern is interpolated, so if $pattern contains something like \, it may even become an error, e.g

C:\>perl
$pattern = "\\";
$variable = "abcde\\fg";
print $variable =~ /$pattern/;
^D
Trailing \ in regex m/\/ at - line 4.
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To prevent this danger of interpolation, use  /(\Q$pattern\E)+/ If you want to capture the multiple expression and not just a single appearance, put braces around and use the inner in a clustering way with ?: e.g $variable =~ s/((?:\Q$pattern\E)+)/..../ or in a better documented way:

$variable =~ s/
  (  # start capturing to $1
    (?: # not capturing, just clustering
      \Q$pattern\E # $pattern in a quoted way
    )
    + # one or more times
  )  # end capturing to $1
/
....
/x;
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If you want to put code at the right hand of the substitution, you could use /e to evaluate code at the right hand sinde, e.g.

  $variable =~ s/((?:\Q$pattern\E)+)/$1.$1.$1/e;
  print $variable;
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The best help may be reading perldoc perlre

Best regards,
perl -e "s>>*F>e=>y)\*martinF)stronat)=>print,print v8.8.8.32.11.32"