I don't know why the switch is not valid there, but anything that complex should be hoisted out of the replacement anyway. This works: 

use strict;
use warnings;
use Switch;

my $text = 'bla fred wilma fuck fred fuck wilma bla fred fredfred';

sub replace_it {
  switch( $_[0] ) {
    case 'fred'  { return 'wilma' }
    case 'wilma' { return 'fred'  }
    die;
  };
}

$text =~ s{(fred|wilma)}{replace_it($1)}eg;

print $text;

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In reply to Re: regex switch trouble by Util
in thread regex switch trouble by spx2

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