#!/usr/bin/perl
use strict;
use warnings;
use autodie;

my %replacements = (
        'user.name@domain.com' => 'uname',
        'user@domain.com' => 'user',
);

open( my $readFile, '<', "sampleFile" );

while ( <$readFile> ) {
# if contains :Calendar and is suffixed with / 
# or :Contacts with same suffix or Users prefixed 
# with / or is an email-address followed by " =
   
if ( m/:Calendar(?=\/)/, 
     m/:Contacts(?=\/)/, 
     m/(?<=\"\/)Users/, 
     m/.+@.+\"\s=/) {
     # then replace every occurrence as in list
       foreach my $key ( sort keys %replacements ) {
            s/\b$key\b/$replacements{$key}/g;
            }
    }
print $_;
}