Made string multiplication more clear in perlintro

[Permik]

Added "repeats strings" in parenthesis to make it more unambiguous.

[khwilliamson]

I'll merge this as soon as we figure out how to show @Permik as a Perl5 contributor. We have always used email addresses, but the one that Perlmik is listed as having is not valid. We should have a way to specify github ids. I refer to this problem in:

#17206 (comment)

[tonycoz]

but the one that Perlmik is listed as having is not valid

I see an email address of permik@users.noreply.github.com which seems valid to me (though not deliverable). I doubt it would be the only undeliverable address in AUTHORS.

[Permik]

I've since added an email to my profile and you can that as the email.
But it's great that this issue has been identified.

[jkeenan]

Picked up contributor's email address from GH profile; added it to p.r. and AUTHORS. Pushed to blead in commit a3d126f.

Thank you very much.
Jim Keenan