PSQL Syntax errors running PL/SQL scripts

Hi,

I am trying to run SQL scripts creating schema in PSQL [PostgreSQL
7.4.3]
and getting tons of errors, mostly "syntax error at or near
character..."
Complains about CONSTRAINTS, Prompt, Set, Local, CREATE, '(', ')' ,...
Also many errors "relation ... already exists"
[I guess, if DROP failed]

My script runs fine with Oracle 8i/9i.

Is PostgreSQL so much different from PL/SQL ?

Any good syntax reference for PostgreSQL ?

Thank you in advance,
Oleg.