use strict;
use warnings;

open my $numberFH, q{<}, \ <<EOD or die qq{open: $!\n};
123456789
567898760
154216722
763498126
EOD
chomp( my @numbers = <$numberFH> );
close $numberFH or die qq{close: $!\n};

my $rxFindTrans = do{
   local $" = q{|};
   qr{(@numbers)};
   };

open my $transFH, q{<}, \ <<EOD or die qq{open: $!\n};
some rubbish
lines
<BEGIN Transaction>
blurfl 154876543
<END Transaction>
more rubbish
<BEGIN Transaction>
the one we want 154216722
with more stuff
<END Transaction>
<BEGIN Transaction>
blargh 54211548
<END Transaction>
EOD

{
    local $/ = qq{<END Transaction>\n};
    while( <$transFH> )
    {
        s{.*(?=<BEGIN Transaction>)}{}s;
        next unless m{$rxFindTrans};
        print qq{Found $1 in:\n$_};
        print qq{==================\n};
    }
}

close $transFH or die qq{close: $!\n};

##</code><code>##

Found 154216722 in:
<BEGIN Transaction>
the one we want 154216722
with more stuff
<END Transaction>
==================