Description of problem:
how to reproduce:

#!/bin/sh
curl --silent --fail "https://en.wiktionary.org/w/index.php?title=test&printable=yes" \
| xpath -q -e \
    '//div[@class = "mw-parser-output"]/*/span[@id = "Verb" or @id = "Noun" or @id = "Adjective"]/ancestor::*/following-sibling::ol[1]/li'

Trying to parse wiktionary. messing with xpath just to experiment.
above seems to cause a problem. probably with how xpath buffers stdin?
when using a process substitution as an argument instead of stdin, it seems to work correctly.

Version-Release number of selected component:
perl-XML-XPath-1.42-2.fc28

Additional info:
reporter:       libreport-2.9.5
backtrace_rating: 4
cmdline:        /usr/bin/perl /usr/bin/xpath -q -e //div[@class = "mw-parser-output"]/*/span[@id = "Verb" or @id = "Noun" or @id = "Adjective"]/ancestor::*/following-sibling::ol[1]/li
crash_function: __libc_sigaction
executable:     /usr/bin/perl
journald_cursor: s=eed7f97804554ea880a518462e7c4cbb;i=8afd8;b=eba64ca943464449a349f01ba4ccb9e2;m=5335fb2d5;t=5726432a1d733;x=2ffc37276436acb9
kernel:         4.17.9-200.fc28.x86_64
rootdir:        /
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (1 frames)
 #0 __libc_sigaction at ../sysdeps/unix/sysv/linux/x86_64/sigaction.c:53