Update: I think Roy Johnson has it right -- watch out for the /g flag.

Something else is wrong:

>perl -demo

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `perldoc perldebug' for more help.

main::(-e:1):   mo
  DB<1> $sentence = 'sdfsdfsdf foo asdfklj bar ;alkdjdf'

  DB<2> x $sentence
0  'sdfsdfsdf foo asdfklj bar ;alkdjdf'
  DB<3> p "match" if $sentence =~ /foo/ && $sentence =~ /bar/
match
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Either $sentence doesn't contain what you think it does, or you haven't run the code you posted. Or you need the /m flag. Or something else.

Please post the actual code (or better, a minimal example that behaves the same way), including the value of the variable involved in the match.