The following code: 
use strict;
use warnings;

my $string = "aDescriptor.Type = {\@see Star.Awt.Win#TOP}";
print( "Original:$string\n" );
$string =~ s/
             {\@see\s+((\w+\.)+)(\w+)\#(\w+)}
            /
             "<idl package=\""
             . lc($1)
             . "\" name=\"$3\" anker=\"$4\">"
            /gex;
print( "Updated:$string\n" );

[download]

..produces the following output.. 

Original:aDescriptor.Type = {@see Star.Awt.Win#TOP}
Updated:aDescriptor.Type = <idl package="star.awt." name="Win" anker="
+TOP">

[download]

Update: holli has the best answer below. I suspected there was an in-place capitalisation modifier, and clearly this is the best solution.

In reply to Re: Regexp matched part to lower case by monarch
in thread Regexp matched part to lower case by tomson

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