config_programs.diff

diff --git a/config/programs.m4 b/config/programs.m4
index 358e4e9..8ccae8c 100644
--- a/config/programs.m4
+++ b/config/programs.m4
@@ -69,7 +69,7 @@ else
         echo '%%'  > conftest.l
         if $pgac_candidate -t conftest.l 2>/dev/null | grep FLEX_SCANNER >/dev/null 2>&1; then
           pgac_flex_version=`$pgac_candidate --version 2>/dev/null`
-          if echo "$pgac_flex_version" | sed ['s/[^0-9]/ /g'] | $AWK '{ if ([$]1 = 2 && [$]2 = 5 && [$]3 >= 4) exit 0; else exit 1;}'
+          if echo "$pgac_flex_version" | sed ['s/[.a-z]/ /g'] | $AWK '{ if ([$]1 == 2 && ([$]2 > 5 || ([$]2 == 5 && [$]3 >= 4))) exit 0; else exit 1;}'
           then
             pgac_cv_path_flex=$pgac_candidate
             break 2