Well I never have tried to profile here's my first try. I compiled with ghc --make -O -prof -auto-all chk_dwlds.hs I've run the program with: ./chk_dwlds \+RTS -p \-RTS and got this .prof file Tue Oct 21 15:01 2008 Time and Allocation Profiling Report (Final) chk_dwlds +RTS -p -RTS total time = 19.62 secs (981 ticks @ 20 ms) total alloc = 19,090,366,024 bytes (excludes profiling overheads) COST CENTRE MODULE %time %alloc run_file Main 67.2 96.5 check_line Main 31.5 2.5 sumcount Main 1.3 1.0 individual inherited COST CENTRE MODULE no. entries %time %alloc %time %alloc MAIN MAIN 1 0 0.0 0.0 100.0 100.0 main Main 238 1 0.0 0.0 100.0 100.0 sumcount Main 242 1 0.0 0.0 0.0 0.0 run_file Main 241 1764 67.2 96.5 100.0 100.0 check_line Main 244 1944781 31.5 2.5 31.5 2.5 sumcount Main 243 1764 1.3 1.0 1.3 1.0 main Main 247 0 0.0 0.0 0.0 0.0 filter_reg Main 248 0 0.0 0.0 0.0 0.0 CAF Main 232 10 0.0 0.0 0.0 0.0 check_line Main 246 2 0.0 0.0 0.0 0.0 regexp Main 245 1 0.0 0.0 0.0 0.0 main Main 239 0 0.0 0.0 0.0 0.0 filter_reg Main 240 2 0.0 0.0 0.0 0.0 CAF Text.Read.Lex 209 8 0.0 0.0 0.0 0.0 CAF GHC.Read 204 1 0.0 0.0 0.0 0.0 CAF GHC.Float 203 3 0.0 0.0 0.0 0.0 CAF GHC.Int 198 1 0.0 0.0 0.0 0.0 CAF GHC.Handle 184 7 0.0 0.0 0.0 0.0 CAF System.Posix.Internals 168 7 0.0 0.0 0.0 0.0 CAF System.Directory 125 1 0.0 0.0 0.0 0.0 Regards Friedrich