while (<DATA>) {
    if (m/^copy\s+.*?\s+(.*?\_.*?)$/) {
        print "$1\n";
    }
}

__DATA__
copy xxxxxx_/cpu     b_relCAP_R3.0-1_INT5_xxxxx_cpu_p1
copy xxxxxxxx_/va_xxx_parameters    b_relCAP_R3.0-1_INT5_xxxxx_va_xxx_parameters_p1
copy xxxxxxxx_/xxxxxxx_view.tcl      b_relCAP_R3.0-1_INT5_xxxxxx_view.tcl_p0
copy xxxxx_/xxxxxarchivetool.jar   b_relEARLY_DROP1_xxxxxarchivetool.jar_xx

b_relCAP_R3.0-1_INT5_xxxxx_cpu_p1
b_relCAP_R3.0-1_INT5_xxxxx_va_xxx_parameters_p1
b_relCAP_R3.0-1_INT5_xxxxxx_view.tcl_p0
b_relEARLY_DROP1_xxxxxarchivetool.jar_xx