Perhaps the following will work for you:

use strict;
use warnings;

my ( @array, %seen );
while ( my $line = <DATA> ) {

    if ( $line =~ /(amazing\.\S+)/ and not $seen{ lc $1 }++ ) {
        push @array, $line;
        #print $line;
    }
}

print for @array;

__DATA__
Today is amazing.nice day 
Today is amazing.nice but still I haven't done anything 
Yesterday was just a normal day 
Tomorrow probably will be amazing.new day

[download]

Output:

Today is amazing.nice day 
Tomorrow probably will be amazing.new day

[download]

$1 captures amazing\.\S+ and using lc on the hash key helps insure case is not significant in uniqueness.

Hope this helps!

In reply to Re: How to ignore lines that match certain string after it is matched for the first time within a same file by Kenosis
in thread How to ignore lines that match certain string after it is matched for the first time within a same file by Ben328

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