The key is two get the whole file into one scalar( the first 'while' loop). Then the 'g' modifier ( the condition in the second 'while' loop ) will keep the place of the last match found and continue from there until there are no matches found.

open( FH, "filename" ) || die "couldn't open\n";

while ( <FH> ) {
    $data .= $_;
}

while ( $data =~ m/PATTERN/g ) {
    # executed code
    # executed code...etc.
}
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-kel