for example:

1. Input file:


My name is $str1 I live in $str2
I like to eat $str1

2. Perl script

#! /usr/local/bin/perl

$str1 = "MIKE";

open(DB,"list.txt") || die "ERR: failed to open DB\n";
@all_lines = <DB>;
close(DB);

@found = grep(/^My/,@all_lines);

print @found,"\n";

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