Disclaimer: I'm not a developer so I might be wrong.

1. U+0024 is $.
2. There is [my $hDollar = &EncodeInput("\$");](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$129)
3. In [if ($Line !~ /^\s*$/) {](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$568), $Line is from: 0 till: 24 color:orange text:"[[Írán]]" (24)
4. We hit [$Line = &EncodeInput($Line);](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$569).
5. We enter the [EncodeInput](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$5174) subroutine.
6. We run [$text =~ s/([\`\{\}\%\&\@\$\(\)\;\=])/"%" . sprintf ("%X", ord($1)) . "%";/ge;](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$5180) and $Line becomes from: 0 till: 24 color:orange text:"[[Írán]]" %28%24%29%
7. We hit [$Line =~ s/($hDollar[a-zA-Z0-9]+)/&GetDefine($Line,$1)/ge;](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$572). Our string includes %24 due to encoding the opening bracket.
8. We match the regex about $hDollar and get into the [GetDefine](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$703) subroutine.
9. In [$const = lc($const);](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$706) , $const = %24%29
10. In [my $value = $Consts{ lc($const) };](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$707), $value remains undefined
11. We bail out in [if (!defined($value)) { &Error("Unknown constant. 'Define $const = ... ' expected."); return ($const); }](https://phabricator.wikimedia.org/diffusion/ETLN/browse/master/EasyTimeline.pl$708)

I'd recommend to use the Graph extension instead of the EasyTimeline extension. Or to fix the regex in step 6.

Change #1053073 had a related patch set uploaded (by Pppery; author: Pppery):

[mediawiki/extensions/timeline@master] Parse $Define calls before encodeInput so that (24) isn't encoded and mangled

https://gerrit.wikimedia.org/r/1053073

Change #1053073 merged by jenkins-bot:

[mediawiki/extensions/timeline@master] Parse $Define calls before encodeInput so that (24) isn't encoded and mangled

https://gerrit.wikimedia.org/r/1053073