perl -ne 'while (/(\w*_\w*)/g) { print "$1\n";}' code_file(s)

##</code><code>##

perl -ne 'BEGIN { my %hash; }; END { print map { "$_\n"} keys %hash} while (/(\w*_\w*)/g) { $hash{$1}=1};' code_file(s)

##</code><code>##

no_wait
ZERO_TABLE_SIZE
subpart_name
segment_config
__END__
skip_table_list
rnc_dspp_dspresu
range_end
dry_run
gp_partition_drop
keep_empty
ignore_table_list
get_lock
FULL_DATE_FORMAT
get_summarised_days
log_init
tv_interval
get_partition_row_count
drop_agg_level
table_name
total_table_size
keep_summarised
summarisation_log
DATE_FORMAT
get_config
MAX_CACHE_TIME
lock_table
skip_tables
GPM_BIN
day_count
drop_daily_agg_level
lock_attempt
get_dbh
get_drop_partition_list
agg_level
lock_type
schema_name
_
site_perl
empty_only
partition_name
range_start
drop_partition
keep_unclassified
time_zone
pm_nsn_3g_ran
row_count
GPI_RECOVER_BACKLOG