QMake uses its own syntax for variable references.
VAR = foobar
=> Assign value to variable when qmake is run$$VAR
=> QMake variable’s value at the time qmake is run$${VAR}
=> QMake variable’s value at the time qmake is run (identical but enclosed to separate from surrounding text)$(VAR)
=> Contents of an Environment variable at the time Makefile (not qmake) is run$$(VAR)
=>Contents of an Environment variable at the time qmake (not Makefile) is run
Try it like this
MYPATH = /lib/aaa/bbb
unix:!macx:!symbian: LIBS += -L$${MYPATH}