my $content = get $url;

##</code><code>##

*.*$left_string $unknown_search_sting $right_string*.*\n

##</code><code>##

"blablaaaa_SES_bbbblala"
"reettaaa_SOS999_bbbtzz"
"wertzaaa_T541_bbbaqyyyyyyy"
"ffaaa_SES_bbbwwwwwwwww"

##</code><code>##

$left_string = "aaa_"
$right_string = "_bbb"

##</code><code>##

SES 2
SOS999 1
T541 1