invalid command name "pg_connect" on tcl/tk script

hi,

i'm using redhat 6.0, postgresql 6.5 and libpgtcl.
i'm really confused, i can't make connection script
with tcl/tk to postgresql back end.

the script always wrong, and always appear
error  " invalid command name "pg_connect" 

why couldn't i write pg_connect command properly ?

what's going on ?

any one can help me to give me sample script to connect
to postgresql back end with tcl/tk ?

thanks