"Maximally one underscore", like "maximally n anything", is easiest done adding a negative lookahead after the start anchor: 

/^(?!.*_.*_)\w*[A-Za-z]\w*$/

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(That is also the most readable way, IMO, and not too slow, though if execution speed is an issue, doing it as a single regex is probably wrong anyway.)

print "Just another Perl ${\(trickster and hacker)},"
The Sidhekin proves Sidhe did it!

In reply to Re: A single regex by Sidhekin
in thread A single regex by kiat

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