$path_unix = 1 if ($path =~ m#(?<=\^)/#);
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Well, that code will not generate an error for any perl since v5.6.1 -- you need to show us what program you're executing

Thanks for the reply. I have given more info in my latest post below. I am trying to build perl 5.14.1 from source on an AIX system. While doing a make, the miniperl seems to complain about this regular expression. Exact command and error are given below:

# make
        `sh  cflags "optimize='-O'" perly.o`  perly.c
          CCCMD =  cc -q32 -DPERL_CORE -c -D_ALL_SOURCE -D_ANSI_C_SOUR
+CE -D_POSIX_SOURCE -qmaxmem=-1 -qnoansialias -DUSE_NATIVE_DLOPEN -DNE
+ED_PTHREAD_INIT -I/usr/local/include -q32 -D_LARGE_FILES -qlonglong  
+-O
        cc -q32 -o miniperl -brtl -bdynamic -L/usr/local/lib -b32 -bma
+xdata:0x80000000    gv.o toke.o perly.o pad.o regcomp.o dump.o util.o
+ mg.o reentr.o mro.o keywords.o hv.o av.o run.o pp_hot.o sv.o pp.o sc
+ope.o pp_ctl.o pp_sys.o doop.o doio.o regexec.o utf8.o taint.o deb.o 
+universal.o globals.o perlio.o perlapi.o numeric.o mathoms.o locale.o
+ pp_pack.o pp_sort.o    miniperlmain.o opmini.o perlmini.o -lbind -ln
+sl -ldl -lld -lm -lcrypt -lpthreads -lc
          ./miniperl -w -Ilib -MExporter -e '<?>' || make minitest
          ./miniperl -Ilib autodoc.pl
          ./miniperl -Ilib -Idist/Cwd -Idist/Cwd/lib pod/perlmodlib.PL
+ -q
Sequence (?<... not terminated in regex; marked by <-- HERE in m/(?< <
+-- HERE =\^)// at dist/Cwd/Cwd.pm line 697.
Compilation failed in require at lib/FindBin.pm line 98.
BEGIN failed--compilation aborted at lib/FindBin.pm line 98.
Compilation failed in require at pod/perlmodlib.PL line 8.
BEGIN failed--compilation aborted at pod/perlmodlib.PL line 8.
make: 1254-004 The error code from the last command is 255.


Stop.
#
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