One lamented aspect of Perl is that regexes get really hard to read. ....

If you learn to regex, they're really easy to read :)

why not use a sigil ...

Because its not on the standard keyboard!

Also, its a delimiter not a sigil

Which is why I prefer to use @ for quoting like s@@@ </sarcasm>

But seriously, this is exactly why i prefer \ or «

$ perl -MO=Deparse -e " s\\\g "
s///g;
-e syntax OK

$ perl -MO=Deparse -e " s«««g "
s///g;
-e syntax OK
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or even </sarcasm>

But seriously, between balanced delimiters like

perl -MO=Deparse -e " s {}//g "
perl -MO=Deparse -e " s {}\\g "
perl -MO=Deparse -e " s {}vvg "
perl -MO=Deparse -e " s {}()g "
perl -MO=Deparse -e " s {}[]g "
perl -MO=Deparse -e " s {}<>g "
perl -MO=Deparse -e " s<><>g "
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I stick to keyboard characters

s///x
s===x
s,,,x
s!!!x
s~~~x
s>>>x
s}}}x

and the special case s'''x

The x means magic