use warnings;
use strict;

while (my $line = <DATA>) {
    if ($line =~ /(\S+)/) {
        my $libn = "$1.lib";
        print "$libn\n";
    }
}

__DATA__
b05_ln_rmmm_0.85v_0.00c_core   /p/ldb/ln/b05_ln_rmmm_0.85v_0.00c_core.ldb:b05_ln_rmmm_0.85v_0.00c_core.ldb
b05_nn__rmmm_g9v_098c_core   /p/ldb/nn/b05_nn__rmmm_g9v_098c_core.ldb:b05_nn__rmmm_g9v_098c_core
b05_un_rsss_0.66v_0.44c_core   /p/ldb/un/b05_un_rsss_0.66v_0.44c_core.ldb:b05_un_rsss_0.66v_0.44c_core