I am using PICBasic Pro in my example (this is a MeLabs compiler site after all!). That example WILL compile with the command line...

pbp -p16F84A Filename

All I did was alias PortB.0 to LED, and use LED thereafter... applying this to your example...

Code:
    @ DEVICE pic16F84A, XT_OSC
    @ DEVICE pic16F84A, WDT_ON
    @ DEVICE pic16F84A, PWRT_ON
    LED var PortB.0
    AntiLED var PortB.1
    TRISA=%00000000
    TRISB=%00000000
Loop:
    High LED
    Low AntiLED
    Pause 500
    Low LED
    High AntiLED
    Pause 500
    Goto Loop
of course you can always simplify the whole (original) loop...
Code:
Loop:
    Toggle LED
    Pause 500
    Goto Loop
Aliasing you will find in your PBP manual. TRISA/TRISB you will find in the PICs Datasheet, and @ DEVICE you will find here...

http://www.picbasic.co.uk/forum/showthread.php?t=543