Try it like this: 
$RGX_EVENTID = qr{\A.*? %(.*?): }xms;
if ( $current_line =~ /$RGX_EVENTID/ ) {
    print "got event_id //$1// from input //$_//\n";
}

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Note the use of the qr operator to assign a regex-like string to $RGX_EVENTID, and the use of normal regex match delimiters around that variable when applying the match to another string. (You need to be careful about using regex delimiters that either don't occur within the regex itself, or are properly escaped when they do occur.)

Also, I think it's better to update your OP to fix the formatting there, rather than creating a reply that fixes the formatting.

Update: forgot to mention... Welcome to the Monastery! "OP" refers to "original post" (top of the thread).

In reply to Re^2: store regex in hash by graff
in thread store regex in hash by salp

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