You're not using the fast lookup properties of a hash. Let $ipre be the regular expression you use for recognising ip addresses when you build %hosts. Make sure it captures the ip in $1. Reading INFILE line by line, and writing FQDN as we go, 

{
    local( *INFILE, *FQDN, $_);
    open INFILE, '< /path/to/longwood.pix' or die $!;
    open FQDN, '> /path/to/fqdn.pix' or die $!;
    while (<INFILE>) {
        s/$ipre/(exists($hosts{$1})?$hosts{$1}:$1)/eg;
        print FQDN $_ or die $!;
    }
    close FQDN or die $!;
    close INFILE or die $!;
}

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After Compline,
Zaxo

In reply to Re: Search and replace in an array using data in hash by Zaxo
in thread Search and replace in an array using data in hash by monger

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