{
    local $_= <DATA>;
    while(  defined $_  ) {
        chomp;
        s/(.)G57/$1\nG57/g;
        print $1   if  s/(.*\n)//s;
        if(  ! /G5?$/  ) {
            print $_,$/   if  "" ne $_;
            $_= <DATA>;
        } else {
            my $next= <DATA>;
            last    unless  defined $next;
            $_ .= $next;
        }
    }
    print $_,$/;
}
__END__
dasdfdafdsfadfdfaG57ewefdsfsdfsG
57dfadfasdfasdfsffdasG57dfsafdsf
sG57dfafdafdsfadfafdfasdfasdfasf
dafdfasdfasdfdsafasdfsdafasdfads
dfadfasfdsdfadfasdfasfdadsfasfdd
G57dsafdsfasdfadsfasdfadfadfadff
dfdf

[download]

This produces: 

dasdfdafdsfadfdfa
G57ewefdsfsdfs
G57dfadfasdfasdfsffdas
G57dfsafdsf
s
G57dfafdafdsfadfafdfasdfasdfasf
dafdfasdfasdfdsafasdfsdafasdfads
dfadfasfdsdfadfasdfasfdadsfasfdd
G57dsafdsfasdfadsfasdfadfadfadff
dfdf

[download]
rather than what you asked for because it doesn't "join" lines unless it has to in order to match the string.

Update: This node briefly showed incorrect code because I forgot to paste the tested code back in.

        - tye (but my friends call me "Tye")

In reply to (tye)Re: How to look for patterns in a file and create a CR by tye
in thread How to look for patterns in a file and create a CR by juo

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