$text =~ s/\Q$_\E/$fixers{$_}/g
   for keys %fixers;

##</code><code>##

my ($re) = map qr/$_/,
           join '|',
           map quotemeta,
           keys %fixers;

while (...) {
   ...
   $text =~ s/$re/$fixers{$_}/g
      for keys %fixers;
   ...
}

##</code><code>##

use List::Regexp qw( );

my $re = List::Regexp->new()->list2re( keys %fixers );

while (...) {
   ...
   $text =~ s/$re/$fixers{$_}/g
      for keys %fixers;
   ...
}