in reply to Grepping from an Array using a variable as the pattern to be matched

perlre, perlretut
"." means any character. 

/\.\Q$classType\E\.\Q$yearMonth\E.{4}00\.XXX_XXXXpm\z/

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or 
/^.{4}\.\Q$classType\E\.\Q$yearMonth\E.{4}00\.XXX_XXXXpm\z/

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In Section Seekers of Perl Wisdom