Like you, I'm a bit confused about just what perlancar is doing (of course, no example code is given). In Perl as in life, there are a lot of ways to 'insert' things into other things, not all of which are appropriate in a given situation. I, also, don't understand why a regex cannot be defined as a simple string and/or qr-ed from the git-go.

... "It's not just the pattern, but the modifiers that must be compared".

But modifiers can be included within a string or qr regex definition (and IMHO, should only be used in this way in the case of the  /i modifier).

c:\@Work\Perl>perl -wMstrict -le
"print $];
 ;;
 my $rxs = '(?i) (?: a|b)';
 my $rx  = qr/$rxs/xms;
 print $rx;
"
5.008009
(?msx-i:(?i) (?: a|b))

c:\@Work\Perl\monks\>perl -wMstrict -le
"print $];
 ;;
 my $rxs = '(?i) (?: a|b)';
 my $rx  = qr/$rxs/xms;
 print $rx;
"
5.014004
(?^msx:(?i) (?: a|b))
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