Ok, I'll play along.. I don't like obtuse code, so I use a lot of whitespace.
and my last issue was with the modifiers, which ended up needing eval().

if (startsWithIgnoreCase(trim($expstr),"s") || startsWithIgnoreCase(tr
+im($expstr),"m")) 
{
   # split the string 
   my @t = split( /\//, $expstr); 
   if(startsWithIgnoreCase(trim($expstr),"s"))
   {
      if(@t>3)
      {
         $t[3]=~s/e//g;
         SyntaxDebug("new regex modifier parameter=".$t[3]."\n");
         if($debugFlag==$true)              # 1.52
         {
            use re 'debug';
            eval("$expdata=~ s/$t[1]/$t[2]/".$t[3] .";");
            $k = $expdata;
         }
         else
         {
            eval("$expdata=~ s/$t[1]/$t[2]/".$t[3] .";");
            $k = $expdata;
         }
      }
      else
      {
         if($debugFlag==$true)              # 1.52
         {
            use re 'debug';
            $expdata=~ s/$t[1]/$t[2]/;
            $k = $expdata;
         }
         else
         {
            $expdata=~ s/$t[1]/$t[2]/;
            $k = $expdata;
         }
      }
     
      SyntaxDebug("substitution=" . @t . " result=". $k . "\n");
   }
   else
   {
      if($debugFlag==$true)              # 1.52
      {
         use re 'debug';

         $expdata=~ m/$t[1]/;
         $k = $$expResult;
      }
      else
      {
         $expdata=~ m/$t[1]/;
         $k = $$expResult;
      }
      SyntaxDebug("match=" . @t . " result=". $k . "\n");
   }
}
else
{
 if($debugFlag==$true)              # 1.52
 {
    use re 'debug';

    $expdata=~$expstr;
    $k=$$expResult;
 }
 else
 {
    $expdata=~$expstr;
    $k=$$expResult;
 }
 if (!defined($k)) 
 {
    $k=$emptyString;
 }

 SyntaxDebug("parse expr='".$1."' k='".$k ."'\n");
}
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thank you Sam