My first JAPH:
The following is legal, and produces output, in BASIC, Befunge, JavaScript (place between <SCRIPT> </SCRIPT> tags in an HTML file) and Perl. 
'11';//;#  76+v,g4-\+0*55:<p0*73+5-*72p0*64*69p1*5 <
'';//;#  japh >:1- JAPH \#^_$$"egnufeB">:#,_7>88*:6^
'0'?eval("function print(japh){document.write(japh"+
''+".replace(/Perl/,'JavaScript'))}",'   '):$_=qq+0;
eval("print('Just Another Perl Hacker.')"),";\x22+;"
''/*";$\=$/;             eval               ;__END__
SUB eval (ja$,ph$)
   PRINT MID$(ja$, 8, 13); "BASIC"; MID$(ja$, 25, 8)
END SUB  '                                Dedalus */

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In reply to Polyglot Japh by Dedalus

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